Looking for thoughts and opinions.

[LetMyBeatPound]

It's been about a week and I've been going over different idea's for this box I am going to build for the two FU 18"s I'm gonna order on Monday. I've pretty much decided on a 4th order with 3:1 ratio because the person I talked to from the FU Audio Facebook page said they do best set up like that. So what I've come up with is:

4ft wide x 3ft long x 2 1/2 ft tall

This is rough estimate but 26 cft gross volume but 20 cft net volume

My port is gonna 10in by 16in x 5in deep, sould be at about 38hz tuning if I followed directions right, not completely sure cuz of internal/external volume and displacement figures.

My sealed up section should be like 9in x 46in x 29in and around 4.5 to 5 cft...

This is still all very rough draft, but I'm am trying to see if I'm headed in the right direction.

The only thing I may have messed up is the tuning number because I think the formula I used was as if the port was to 20 cft and not 15 cft the net volume after displacement of the ported chamber. But if that is how I'm supposed to figure the tune by just the ported chamber size then the port size is 5.5in x 14in x 6in deep and that makes its 35hz tho I read tuning for 4th orders should be around 40hz, but I want more lower bass than the highs if I'm understanding this right...

Thanks in advance for any input! Good, bad, or indifferent... I wanna hear it all.

Sincerely LetMyBeatPound

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[LetMyBeatPound]

Probably should mention that they will be rear firing, and the port facing forward, tearing out my middle bench seat and putting in 2 Civic seats for my rear seats so I can make my port fire your front between all the seats... Really would like some feedback, thanks!

 

[Boomin_tahoe 5,000+ posts]

Building a 4th isn't as simple as it is/sounds.

Why not wall them....flat wall keep it simple.

 

[Jeffdachef 5,000+ posts]

It's been about a week and I've been going over different idea's for this box I am going to build for the two FU 18"s I'm gonna order on Monday. I've pretty much decided on a 4th order with 3:1 ratio because the person I talked to from the FU Audio Facebook page said they do best set up like that. So what I've come up with is:4ft wide x 3ft long x 2 1/2 ft tall

This is rough estimate but 26 cft gross volume but 20 cft net volume

My port is gonna 10in by 16in x 5in deep, sould be at about 38hz tuning if I followed directions right, not completely sure cuz of internal/external volume and displacement figures.

My sealed up section should be like 9in x 46in x 29in and around 4.5 to 5 cft...

This is still all very rough draft, but I'm am trying to see if I'm headed in the right direction.

The only thing I may have messed up is the tuning number because I think the formula I used was as if the port was to 20 cft and not 15 cft the net volume after displacement of the ported chamber. But if that is how I'm supposed to figure the tune by just the ported chamber size then the port size is 5.5in x 14in x 6in deep and that makes its 35hz tho I read tuning for 4th orders should be around 40hz, but I want more lower bass than the highs if I'm understanding this right...

Thanks in advance for any input! Good, bad, or indifferent... I wanna hear it all.

Sincerely LetMyBeatPound

If you dont know how to build a 4th then dont try...

Your tuning is purely based on your sealed's resonance not what you prefer... If you dont have a termlab/RTA or whatver meter, you should not be building 4ths. You need to tune exactly at the sealed portion's resonance to get maximum output AND bandwidth. Being off will just make the whole enclosure a complete flop as in good luck breaking 145db.

 

[LetMyBeatPound]

Could either of you recommend a type and style. I consider myself to be fairly capable of building with wood, I worked as a framer on an construction crew for a few years. 2 FU 750 18s on a 2000w Alphard, so any cubic ft recommendations and what hertz I should aim for for port tuning.